This invention relates generally to systems for monitoring the presence or absence of a patient in or from a bed, wheelchair or the like and more particularly concerns monitoring systems having programmable capability to tailor the system functions to meet the needs of specific mobile monitoring applications.
Presently known monitoring systems, such as those described in earlier U.S. Pat. Nos. 4,484,043 and 4,565,910, have serious limitations of function and operating capability. First of all, they are generally hard-wired and therefore not useful in most mobile applications, especially in long term or home care situations. Since they are intended for use in short term or hospital environment situations, their hard wiring typically provides a delay between switching and activation to permit multiple manipulations of a patient by the staff without triggering an alarm. They require the manual operation of on/off switches to activate the monitoring process. Once activated they must be shut down completely to enable a nurse to move a patient and then manually operated to reactivate the device after return of the patient. But, once activated, patients can, intentionally or inadvertently, trigger the alarm by removing their weight from the system sensor device and then cancel the alarm by returning their weight to the system sensor device. This frequently results in tiresome "cry wolf" attempts by patients to get attention and can even result in disregard of a valid emergency situation by the monitoring staff. They are not locally modifiable by the monitoring staff to accommodate the needs of a particular patient and/or environment. They generally offer no selection of tonal variations in their audio alarm, no selection of time delay increments in their activate and/or alarm modes and no choices as to the operational steps required to disarm and re-arm the device. A further problem encountered in present monitoring systems is that they employ their on/off switch controls in such a manner that inadvertent disconnection of the sensor device from the system does not cause an alarm. Therefore, the monitoring staff has no assurance that a patient is actually being monitored without repetitive local inspection to assure that the sensor device is properly connected to the system.
It is, therefore, one of the primary objects of this invention to provide a patient monitoring system which is mobile rather than hard-wired. Another primary object of this invention is to provide a patient monitoring system which is suited to long term and/or home care of patients. Still another object of this invention is to provide a patient monitoring system which is programmable on-site by monitoring personnel to adapt the system to each specific patient and environment. It is also an object of this invention to provide a patient monitoring system which is activated by initial pressure on a sensor device rather than by the use of on/off switches. A further object of this invention is to provide a patient monitoring system which can be temporarily deactivated to a "hold" mode by use of a reset control on the unit and which will be automatically reactivated to a "monitor" mode when the patient is returned to the system. Yet another object of this invention is to provide a patient monitoring system in which disconnection of the sensor device from the system will result in a failsafe alarm. And it is an object of the present invention to provide a patient monitoring system which, in its programmable functions, includes variations of type and volume of alarm tones, variation in time delay characteristics and an election to cancel an alarm either by return to the monitored condition by the patient or by an independent disarming activity.